Paul reminds the Thessalonian Christians that Christian life must certainly include what today we would call an ascetic component...
Paul reminds the Thessalonian Christians that Christian life must certainly include what today we would call an ascetic component. This is not about mortifying the flesh, as asceticism is often understood today, but about consciously governing one's spiritual states and thereby determining the course and quality of one's life. It is in this sense that the apostle speaks of the need to "keep one's vessel in holiness and honor," not defiling it with "sexual immorality," which Paul most likely understands as broadly as the ancient prophets understood it.
Indeed, what is life from the Bible's point of view? It is a stream that comes from God and flows through a person, while the person in some mysterious way also abides in it, determining its quality and direction. In the language of the Bible it is called the "soul," although the corresponding Hebrew word, like its Greek equivalent, is often rendered by translators simply as "life," which matches the original meaning. But in this case the point is not life as a flow of events external to a person, but life as something that permeates a person from within, filling him with the dynamic without which the person does not exist.
This inner dynamic is called the "soul," or simply life, and it includes both spirit, including all those movements of the soul that we call higher, and nature, down to such "lowly" things as breathing or blood circulation. But the overall quality of this stream and the predominance in it of the spiritual or natural component are determined by the person himself at the level of his spiritual "I," what the Bible calls the "heart." It is there that a person's spiritual self-determination takes place through his will; there are born the intentions that govern his spiritual life and life in general.
And there, in the heart, the door opens, or, on the contrary, slams shut, through which God's breath of life enters the stream of a person's life, his inner space, and, if we are speaking of Christians, the breath of the Kingdom as well. A person contains this breath insofar as his own life is consciously directed by him, through those same intentions, along the path of the commandments given by God, along the path of the inner Torah. The inner Torah is precisely the vessel that allows God's breath of life and the breath of the Kingdom to abide in a person.
Otherwise, even after sensing this breath and sharing in it, a person will not be able to keep it. The spiritual influence will end, the ecstasy will cease, and the person will return again to his former life, becoming the same as he was before the influence he experienced. A person can change only with his own active participation in the process, when he strives to keep what he receives from God by creating in his inner space a corresponding receptacle, that very "vessel." This is what Paul reminds the Thessalonian Christians of in his letter.